1. Field of the Invention
This invention relates to a drive stage and also to a scanning probe microscope and an information recording/reproducing apparatus using such an drive stage.
2. Related Background Art
The recent invention of the scanning tunneling microscope (hereinafter referred to as STM) made it possible to visually observe an image of the surface of an electrocoductive substance with a degree of resolution of the nanometer level or lower (U.S. Pat. No. 4,343,993) so that now the arrangement of atoms of the surface of metal or semiconductor and the orientation of organic molecules are equally observable. Furthermore, the atomic force microscope (hereinafter referred to as AFM) adapted to observe the surface of an insulating substance with the degree of resolution of the STM has been developed as an extension of the STM technology (U.S. Pat. No. 4,724,318). The scanning near-field optical microscope (hereinafter referred to as SNOM) has also been developed from the STM. It can be used to examine the surface of a specimen by utilizing evanescent light seeping out from the micro-aperture arranged at the micro-tip of the sharp probe of the microscope [During et al., J. Appl. Phys. 59, 3318 (1986)]. Currently, these and other similar microscopes are globally referred to as the scanning probe microscope (hereinafter abbreviated as SPM) and used to measure the tunneling current, the electronic state density, the interatomic force, the intermolecular force, the frictional force, the elastic force, the evanescent light, the magnetic force and other various physical values of the surface of a specimen.
The above described SPM technology is being applied to memories. For example, Japanese Patent Application Laid-Open Nos. 63-161552 and 63-161553 describe a method of recording/reproducing information by means of an STM and a recording medium of a material capable of storing information on the volt-ampere switching characteristic of the recording medium, which may typically be realized in the form of a thin film layer of a xcfx80-electron type organic compound or a chalcogen compound. With the proposed method, a change in the characteristic is made to occur and recorded in a minute region of the recording medium located right below the probe of the STM by applying a voltage higher than a certain threshold level, utilizing the phenomenon that the tunneling current flowing between the probe and the recording medium changes depending on the recording section and the non-recording section of the recording medium. With the proposed method, an information processing apparatus having a recording density of 1012 bits/cm2 can be realized, provided that a bit size of 10 nm in diameter is selected for the recording.
It is also known that a recording medium in the form of a thin film of a metal such as Au or Pt that becomes locally molten or evaporated to produce a projection or a recess on the surface when a voltage exceeding a certain threshold level is applied thereto can be used for recording/reproducing information concurrently.
With any of the above described SPMs, the probe is driven to move relative to the surface of a specimen or a recording medium by a drive stage and the physical interaction between the probe and the specimen is detected in order to obtain an image or record/reproduce information. FIGS. 1 through 3 of the accompanying drawings schematically illustrate known drive stages.
The drive stage shown in FIG. 1 comprises a cylindrical piezoelectric element 1000 and four electrodes 1001 through 1004 arranged on the outer periphery of the cylindrical piezoelectric element in four respective equally divided sectors thereof (although the electrode 1004 is not visible in FIG. 1). A mechanical stage 1005 is connected to the top of the piezoelectric element (although it is separated from the piezoelectric element in FIG. 1). The cylindrical piezoelectric element 1000 can be made to bend by controlling voltages applied to a pair of oppositely disposed electrodes (1001 and 1003 or 1002 and 1004) so as to cause one to expand and the other to contract. The piezoelectric element 1000 can be made to axially extend or contract by applying a same and identical voltage to all the four electrodes. Thus, the piezoelectric element 1000 can be made to extend or contract three-dimensionally by controlling the voltages applied to the four electrodes 1001 through 1004. Then, the mechanical stage 1005 bonded to the top of the piezoelectric element can be driven to move three-dimensionally.
FIG. 2 illustrates a uniaxial drive stage. It comprises a support body 2001 and a mechanical stage 2002 linked to the support body 2001 by means of parallel hinge springs 2003. These components may be integrally manufactured or assembled to produce the drive stage. Additionally, a piezoelectric actuator 2004 is linked to the mechanical stage 2002 and the support body 2001 respectively at the opposite ends thereof. With the illustrated drive stage, the mechanical stage 2002 can be driven to move leftwardly or rightwardly in FIG. 2 relative to the support body 2001 by applying a voltage to the piezoelectric actuator 2004 to make it expand or contract.
FIG. 3 illustrates a drive mechanism disclosed in Japanese Patent Publication No. 6-46246. Referring to FIG. 3, a mechanical stage 3003 is supported by two pairs of parallel hinge springs 3010, 3011 and 3012, 3013 at an end of each of them. The pair of parallel hinge springs 3010, 3011 are connected at the other end of each of them to a Y-axis drive piezoelectric actuator 3005 by way of an auxiliary support body 3001, while the pair of parallel hinge springs 3012, 3013 are connected at the other end of each of them to an X-axis drive piezoelectric actuator 3006 by way of another auxiliary support body 3002.
The auxiliary support body 3001 is supported by the parallel hinge springs 3010, 3011 and also by parallel hinge springs 3014, 3015 arranged perpendicularly relative to the hinge springs 3010, 3011 at an end of each of them, whereas the auxiliary support body 3002 is supported by the parallel hinge springs 3012, 3013 and also by parallel hinge springs 3016, 3017 arranged perpendicularly relative to the hinge springs 3012, 3013 at an end of each of them. All the parallel hinge springs 3014, 3015, the parallel hinge springs 3016, 3017, the Y-axis drive piezoelectric actuator 3005 and the X-axis drive piezoelectric actuator 3006 are connected at the other end of each of them to a substrate 3000.
With the above described arrangement, both the mechanical stage 3003 and the auxiliary support body 3001 are driven to move along the Y-axis as they are supported respectively by the parallel hinge springs 3012, 3013 and the parallel hinge springs 3014, 3015 when the Y-axis drive piezoelectric actuator 3005 is expanded or contracted. On the other hand, the parallel hinge springs 3010, 3011 are highly rigid along the Y-axis and hence move together in that direction. Similarly, both the mechanical stage 3003 and the auxiliary support body 3002 move together along the X-axis when the X-axis drive piezoelectric actuator is expanded or contracted.
Thus, the mechanical stage 3003 follows the motion of the Y-axis drive piezoelectric actuator 3005 and that of the X-axis drive piezoelectric actuator 3006 with complete fidelity so that the two motions do not interfere with each other on the mechanical stage 3003.
Then, the mechanical stage 3003 can be driven to move both in the X-axis and in the Y-axis in any desired fashion by means of the X-axis drive piezoelectric actuator 3006 and the Y-axis drive piezoelectric actuator 3005.
However, with any of the known drive stages of FIGS. 1 through 3, the inertial force generated in the mechanical stage increases as the drive stage is driven to move faster so that the support members will eventually vibrate due to the inertial force.
Then, such vibrations on the part of the support members give rise to blurred images when the drive stage is used for an SPM and information recording/reproducing errors when the drive stage is used for an information recording/reproducing apparatus.
If a heavy support cabinet is used to suppress the vibration, the total weight of the apparatus to a great disadvantage thereof.
Therefore, it is the object of the present invention to solve the above identified problems of the known technologies and provide a drive stage that is compact, lightweight and practically free from vibrations if driven for high speed scanning and also a scanning probe microscope and an information recording/reproducing apparatus realized by using such a drive stage.
According to an aspect of the invention, the above object is achieved by providing a drive stage comprising:
a support body;
a plurality of movable parts movably supported relative to said support body; and
an actuator for driving said plurality of movable parts to move;
said plurality of movable parts being driven by said actuator to move in directions selected to mutually offset the inertial forces generated in the respective movable parts.
According to another aspect of the invention, there is also provided a drive stage comprising:
a plurality of movable parts; and
a plurality of cylindrical piezoelectric elements adapted to move said plurality of movable parts respectively, each of said piezoelectric elements having a plurality of drive electrodes arranged on the outer periphery thereof, said piezoelectric elements being arranged coaxially;
said plurality of movable parts being driven respectively by said piezoelectric elements to move in directions selected to mutually offset the inertial forces generated in the respective movable parts.
According to still another aspect of the invention, there is also provided a scanning probe microscope comprising a stage and a probe arranged vis-a-vis the stage, either the stage or the probe being arranged on the movable parts of the above drive stage, said scanning probe microscope being adapted to observe the surface of the specimen by detecting the physical interaction of the specimen and the probe, while driving the specimen on the stage and the probe to move relative to each other by means of said drive stage.
According to a further aspect of the invention, there is also provided an information recording/reproducing apparatus comprising a recording medium and a probe arranged vis-a-vis the recording medium, either the recording medium or the probe being arranged on the movable parts of the above drive stage, said information recording/reproducing apparatus being adapted to at least either record or reproduce information by applying a voltage between the recording medium and the probe, while driving the recording medium and the probe to move relative to each other by means of said drive stage.